Driving connection



- luy 5, 1927.Il

c. SCHRAMM E'r Al.

DRIVING CONNECTION 1924 4 sheets-sheet 1 Filed -June 4 nflfmmml z nlllrl.

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DRIVING CONNECTION Filed June 4. 1924 4 Sheelts-Sheet 2 INVENTHHSA W@ge/)M WK7N a iff/,

` ATTQBNEY guly 5 1927 c. SCHRAMM ET AL DRIVING CONNECTION Filed June 4.1924 A{sheets-sheet 3 "Wfmmfwu l TTHHHEY Lame@ Emily 5 @27 c, scHRAMM ETAL,

DRIVING CONNECTION Filed June 4, 1924k 4 sheets-snaai 4 Patented July 5,1927.

UNITED STATES 1,634,386 PATENT OFFICE.

CARL SCBRAIM, 0F WIE-ST HARTFORD, AND A:PAUL F. VOKAL, OF HARTFORD, CON-NECTICUT, ASSIGNORS T0 PRATT 85 WHITNEY COMPANY, OF NEW YORK, N. Y., A.

y CORPORATION OF NEW JERSEY.

DRIVING CONNECTION.

Application led`June 4,

Our invention relates to driving connections and particularly to drivingconnections for operating thread grinding machines.

One object of our invention is to provide a driving connection for awork carrying spindle and a lead screw that shall compensate for theback lash between the work spindle and the lead screw.

Another object of our invention is to provide a driving connection for athread grinding machine that shall be provided with a loose connectionso constructed as to compensate for back lash and insure correctrelative position between the grinding wheel and the work when the workand the grinding wheel are axially moved relatively to each other in`either direction.

In many machines, it is essential to maintain the cutting tool and thework in correct relative position. Thus in grinding a thread, it isessential to maintain the rotating work or thread in a correct relativeposition with respect to the grinding wheel. In moving the worklongitudinally past the grinding wheel, it is not diliicult to maintainthe grinding wheel in correct position with respect to the threads beingground when the work is being moved in one direction past the grindingwheel. However, upon reversing the longitudinal movement of the work,the back lash in the driving connection between the work spindle andthelead screw changes the relative position of the rot-ating work and thegrinding wheel so as to require a resetting of the work and the wheelwith respect to each other.

-In a machine constructed in accordance with our invention, a looseconnection is provided between either the work carrying spindle or thelead screw to compensate for the back lash in thedriving connectionserving to operate the machine. Preferably the loose connection isprovided between the work carrying spindle and the driving connection.In practicing our invention, the loose' connection serves to preventrotation of the work carrying spindle upon reversal in the direction ofrotation4 of the spindle and the leadscrew until the lead screw has beenrotated sutcient to take up all back lash in the driving connection. Inthe conl struction above set forth, it will be noted no means is usedvto prevent back lash but means is provided for compensating for the1924. Serial No. 717,794.

' invention.

Fig. 2 is an end elevational view of the machine shown in Fig. 1.

Fig. 3 is a detail view illustrating the wheel dressing slide.

Fig. 4`is a detail view of the means for controlling the wheel feedingmovements.

Fig. 5 isa view partially in section along the line 5 5. of Fig. 4.

Fig. 6 is a sectional view along theline -6 6 of Fig. 1. i

Fig. 7 is a sectional view along the line 7-7 of Fig. 6.

Fig. 8 is a sectional view through the loose connection shown in Fig. 1between the work carrying spindle and the driving means.

Fig. 9"is a sectional view along the line 9--9 of Fig. 8.

Fig. 10 1s a detail view ofthe adjusting pin shown in Fig. 8.

Fig. 11 is a. view partially in section of a second loose connectionadapted to be placed between the work carrying spindle and the drivingmea-ns.

Fig. 12 is a sectional view along the line 12-12 of Fig. 11.

' Fig., 13 is a sectional view along the line 13-13 ofthe looseconnection shown in Fig. 11.

Fig. 14 is a third and the preferred loose connection adapted to` beplaced between the work carrying spindle and the driving means.

Fig. 15 is a sectional view along the line 15-15 of the drivingconnection shown in Fig.v 14.

Fig. 16 is a sectional'view along the line 16-16 of thc drivingconnection shown in Fig. 14.

Fig. 17 is a sectional view through the reversing mechanism.

Fig. 18 is a detail view of partsof the reversing mechanism inhorizontal section.

Referring to the drawings, a thread Aor tap grinding machine is showncomprising a main frame 1 upon which is mounted a work `carryingcarriage 2 and a wheel slide 3.

The carriage 2 is mounted upon suitable guides 4 and 5, and the sllde 3is mounted upon suitable guides 6 and 7. -The carriage 2 carries aheadstock 8, which is preferably fixed to the carriage 2, and atailstock 9 which is adjustable along the carriage 2 on suitableguideways.

An auxiliary wheel slide 10 is supported 0n a suitable uideway in theslide 3, as best shown in ig. 3 of the drawings. A nut 11, whichprojects from the bottom of the auxiliary slide 10, engages a screwshaft 12. TheY screw shaft 12 serves to effect feedingl movement of thewheel slide 3. The auxiliary slide 10 is connected to the wheel slide 3by means of a nut 13 and a screw shaft 14. The nut 13 is iixedly securedto the auxiliar slide 10 and engages the screw shaft 14 which is mountedon the wheel slide 3. Thus, it is apparent rotation of the screw shaft12 serves to operate the wheel slide 3 through the nut 11, auxiliaryslide 10, the nut 13 and the screw shaft 14. The screw shaft 14 isoperated, in a manner to be hereinafter set forth, when the grindingwheel is being dressed.

The wheel slide 3 is provided with a' bracket 15 which serves to supporta wheel supporting plate 16. The bracket 15 is provided with arcuateT-slots 17 which are en- 16 in any set position. The plate 16 isprovided w1th suitable bearings for the wheel spindle 19. The spindle 19carries a grind-- lng wheel 20 and a driving pulley 21. In the'aboveconstruction, it will be noted the plate 16 may be adjusted on thebracket 15 to angularly adjust the grinding wheel 20 with respect to theworkbeing operated upon.

The pulley 21 is connected by a suitable belt 22 to a pulley 23 which ismounted on a power shaft 24. The be'lt 22 extends over two idler pulleys25 which are mounted on the slide 3. A pulley 26, which is mounted onthe main frame 1, is resiliently held in engagement with the belt 22 totake up any slack during the movement of the wheel slide with respect tothe mai frame.

A dressing slide 27 is provlded for carrying a suitable dressingattachment to true the grinding wheel 20. The slide 27 is movable alonga second slide 28 and may be locked to the second slide by means of alever 29a. The movement of the slide 28 is controlled by a hand wheel29. The hand wheel 29 not only serves to effect movement of the slides28 and 27 for dressing the wheel but also serves to effect movement ofthe wheel slide 3 by means of the screw shaft 14. The hand wheel 29 isconnected to a short shaft 30 having a bevel gear wheel 31 mountedthereon. The bevel gear'wheel 31 meshes with a bevel gear wheel 32 whichis mounted on a shaft 33. The shaft 33 'earries aspur gear wheel 34 andis provided with screw threads 35 which engage a nut 36. The nut 36 issecured to the slide 28, as indicated on Fig. 2 of the drawings. Thegear whe-el 34 is connected to a gear wheel 38 which is mounted on andsecured to the screw shaft 14. The gearing between the shaft 33 and theshaft 14 is such as to effect a two to one movement between the slide 28Iand the wheel slide 3. Thus, the dressing slide is moved twice as faras the wheel slide. Accordingly the grinding wheel 20 is always mamtamedin adjusted position with respect to the work being operated no matterthe end thereof, meshes with a spiral gear wheel 45 which is mounted ona shaft 46. The shaft 46 is connected to a gear whec'l 47 by means of asuitable clutch 48. The clutch 48 iscontrolled by a handle 49 which ismounted on a lever 50. The lever 50 is pivoted at 51 and operates alever 52 b v means of an arm 53. The lever 52 is pivotal'ly supported at54 on the main frame 1 and engages a bell crank lever 55. The bell cranklever 55 is provided with a bifureated end ortion which engages a collarformed on t e clutch 48.

The gear wheel 47 meshes with a gear wheel 58 which is mounted on ashaft 59.

The shaft 59 is located directly above the Vwheel 65 which meshes with agear wheel 66 on a short shaft 67. The'shaft 67 carries a pulley 68 forsupplying power to rotate the Work carrying spindle and to effectmovement of the work carrying carriage 2.

The gear wheel 47 not only meshes with the gear wheel 58 but also mesheswith :114.20

gear Wheel 69 which is fixedly mounted on a shaft 70. The shaft 70 alsocarries agear wheel 71 which meshes with the -gear wheel 60 on the shaft59. The gear wheel 71 is ixedly connected to the shaft 70 and is con-`nected to a ratchet wheel 72. Between the ratchet wheel 72 and the gearwheel 69, a cam drum 73 is loose'ly mounted on the shaft 70. The camdrum 73 has a pawl disk 74 secured to it adjacent to the ratchet wheel72. The disk 74 carries a pawl member 75 which is adapted to engage theteeth on the ratchet wheel 72. A. spring member 76 is provided forexerting a force at all times tending to move the pawl 75 into engaement with the teeth on the ratchet wheel 2. Two levers 77 and 78 whichare located on opposite sides of the shaft 70 are provided for engagingthe pawl 75 to move 1t out of engagement with the ratchet wheel. Thelevers 7 7-and 78 are respectively mounted on short shafts 79 and 80which also carry levers 81 and 82. The levers 81 and 82 are joined by aspring member 83 which exerts a force tending to move the levers 77 and78 in the path of movement of the pawl 75. One arm 84 of a bell cranklever 85 is disposed between the levers 81 and 82 and serves to operatethe levers 81 and 82 in accordance with the movement of the'carriage 2.The bell crank lever 85 is connected by a reach rod 86 to a bell cranklever 87. The ,be'll crank lever 87 is o erated by two dogs 88l and 89which are ad]ustably mounted on the' carriage 2. The dogs 88 and 89serve to limit the' extent of movement of the carriage 2.

Assuming the lever 77 to be in .engagement with the pawl 75, as shown inFig. 17 of the drawings, and the pawl to be held out of engagement withthe ratchet wheel 72, the cam drum 73 is held stationary. However, uponengagement between the dog 89 and the bell crank lever 87, the arm 84 ofthe bell crank 85 engages. the lever 81 and moves the lever 77 out ofengagement with the pawl 75. rI`he pawl 75 engages the teeth of theratchet wheel 72 and accordingly the disk 74 and the cam drum.7 3 arerotated with the shaft 70. Such rotation of the disk 74 and the cam drum73 continues until the pawl 75 is enga ed by the lever 78. The lever 78moves t e pawl out of engagement with thel revent further movementvratchet wheel to of the cam drum 3.

Upon engagement between the dog 88 and the bell crank lever 87 at theother end of the movement of the carriage 2, the lever l78 4is moved outof engagement with the pawl 75 to eEect a half rotation of the cam drum73. This last movement of the cam drum is stopped by the lever 77engaging the pawl 75 to disengage it from a ratchet wheel 72. The disk74 is provided with two notches 92 which are fitted t'o a. springpressed plunger 93 to prevent any retrograde movement of the disk 74 andthe cam rum 73.

The cam drum 73 has a cam groove 94 formed therein which operatesa'lever 95 to control the clutch mechanism 62. The clutch mechanism'62,as heretofore set forth, serves to connect either the gear wheel 58 orthe gear wheel 60 to the shaft 59. By such ymeans it is apparent thepulley 68 is rotated in a clockwise or in a counterclockwise direcaroundtwo idler pulleys 100 which are mounted on the carriage 2. -The shaft 98carries a spiral gear wheel 101 which meshes with a spiral gear wheel102 on a shaft 103. The shaft 103 carries a gear wheel 104 which, mesheswith a gear wheel 105 on a shaft 106. The shaft 106 is connected througha. suitable lost motion connection 107 to the driving spindle 108. Theshaft 103 also carries a pinion 109 which meshes .with a gear wheel 110.The gear wheel 110 meshes with a gear wheel 111. The gear wheel 111 isconnected to a glear wheel 112 which ,meshes with gear w y connected tothe lead screw 114 which efects movement of the carrial e 2.

Referring to Figs. 1, 6 an 7 of the drawings, the lead screw 114 isconnected to the carriage 2 by means of a nut 115 which has a worm wheel116 secured thereto. The worm wheel 116, which is lixedly connected tothe nut 115, meshes with a worm 117. The worm 117 is formed on a shaft118. The shaft 118 extends through the front of the machine and has ahand wheel 119 mounted thereon. The hand wheel 119 serves to effectadjustment 0f the carriage 2 with respect to the wheel 20 at will.

The lead screw 12, which operates the wheel slide 3, has a ear wheel 121mounted on it, as shown in igs. 1,` 4 and 5 of the drawings.` The gearwheel 121 meshes with a pinion 122 on a short shaft 123. The shaft 123carries a gear wheel 124 which meshes with a pinion 125 on a shaft 126.The shaft 126 carries a hand wheel 127 for effecting feeding movement ofthe wheel slide 3 at will. The shaft 126 also carries a ratchet wheel128 and a three armed lever 129. One arm 130 of the flever 129 carries apawl 131. A

second arm 132 of the lever carries a pawl 133 and a third arm 134 isconnected b a link 135 to a bell crank lever 136. The ell crank lever136 is operated by a plunger 137.

lThe plunger 137 is operated by means of a dog 138 which is adjustablymounted on the work carrying carriage 2. The dog 138 operates theplunger 137 at each reciprocation of the carriage 2 and accordinglyeffects an oscillating movement of. the three arm lever 129. If the pawl131 is in engagement with the teeth of the ratchet wheel 128, anintermittent feeding movement of the wheel slide 3 will be effected. Ashield 139, which is adjustable on the 'ratchetwheeh serves to limit thetotal feeding t0 any desired eel 113. The gear wheel 113 is fxedamount.The shield 139 extends over the teeth of the ratchet and prevents thepawl 131 from engaging the teeth when the wheel has been fed to apredetermined depth. The arm 132 carries a handle 140 for feeding byhand when so desired. The amount of feed eifectedby the arm 132 .may becontrolled by means of a shield 141 which is supported on the main frameof the machine.

Referring to Figs. 1, 8, 9 and 10, one form of the loosev connection isillustrated for compensating for the back lash in the gearing connectedtothe lead screw 114 and the work spindle 108. The shaft 106, which isconnected to the work spindle 108 through the loose connection 107,projects through a sleeve 144 which is suitably secured to the headstockof the machine. Adjacent to the sleeve 144, an arm 1'45 is keyed to theshaft 106. The arm '145 carries a pin 146 which projects into positionbetween two stop members 147 and 148. The two stop members are mountedon a cup-shaped member 149. The cup-shaped member 149 is keyed to thework carrying spindle 108 as shown in Fig. 8 of the drawings. The pin146 is adjustable in the arm 145 and is held in any set position bymeans of two set screws 150. A collar 151, which is threadably connectedto the sleeve 144, engages a notch in the pin 146 and serves to adjustthe position of the pin in the arm 145. A set screw 152 is provided forholding the collar 151 in any set position on a sleeve 144. It may benoted that the pin 146 may be adjusted by means of the collar 151 evenif the shaft 106 and the spindle 108, are in rotation.

The pin 146 is provided with a tapered surface 153 which is adapted toengage the stop member 147 and a straight surface 154 which is adaptedto engage the stop member 148. The stop member 147 is adjustable in aslot 155 and is provided ywith a tapered surface `156 which isl adaptedto engage the tapered surface 153 on the pin. The stop member 148 may besecured in any one of the holes 157 in the cup member 149 and isprovided with a straight surface for engaging the straight surface 154on the pin 146.

In the above construction, it will be noted, the work carrying spindle108 is rotatedby the pin 146 engaging one of the stop members 147 or148. Inasmueh as the pin 146 does not simultaneously engage the two stopmembers 147 and 148, it is apparent a reversal in the directionofrotationiof the shaft 106 permits the driving connection to operatefor a limited time before the work carrying spindle 108 is rotated.Thus, compensation is effected for the back lash between the lead screw114 and t-he work spindle 108. The amount of loose connection betweenthe shaft 106 and the work spindle 108 may be roughly adjusted byvarying the position of the' two stop members 147 and 148. A fineadjustment of the 'loose connection may be 'effected by varying theposition of the pin 146 in the arm 145.

Referring to Figs.' 11, 12 and 13 of the drawings a modification of ourinvention is illustrate The shaft 106 projects through a cup-shapedmember v160 which is secured to the carriage 2. A hub member 161, whichis suitably pinned to the shaft 106, is disposed adjacent the cup member160 and has teeth 162 formed on its periphery. A spider member 163carries a number of pairs of pinions 164 and 165. v Each pair of'pinions164 and 165 are rotatably mounted on a shaft 166 which is suitablysecured to the spider member 163. Each of the pinions 165 meshes withthe teeth 162 formed on the hub member and with teeth 167 which areformed on the cup member 160. Each of the pinions 164 meshes with teethwhich are formed on the inside periphery of a ring shaped worm wheel 168and with teeth 169 which are formed on a hub member 170. The hub member170 is rotatably mounted on the shaft'106 and carries a pin 171 whichprojects through a slot 17 2 which is formed in a second cup-shapedmember 173. The cup-shaped member 173 is fixedly connected to the shaft106. The ring shaped worm wheel 168 is located between and supported onthe two cup members 160 and 173, as best shown in Fig. 11 of thedrawings. The cupshaped member 173 carries a pin 175 which is located atthe same distance from the shaft 106 as the pin 171 is located. The twopins 171 and 175 are adapted to engage an arcuated lug 176 whichprojects from a disk 177. The disk 177 is lixedly connected to the workcarrying spindle108. A suitable Worm shaft 178 is provided for effectingoperation of the worm Wheel 168. j

The pin 175 engages one end of the lug 176 to effect rotation of thespindle 108 in one direction and the other end of the lug 17 6 to effectrotation of the spindle in a reverse direction. The position of the pin171 in the Slot 172 may be adjusted to provide any amount of looseconnection between the shaft 106 and the work carrying spindle 108. Whenthe worm shaft 178 and the Worm wheel 168 are held stationary, it isapparent the pin 171 rotates with the shaft 106. Such operation isapparent inasmuch as the cup-member 160 and the worm Wheel 168 are heldstationary. The pinions 164 and 165 rotate at the same speed andconsequently the hub member 170 is compelled to rotate at the same speedas the hub member 161. The rotation of the worm wheel 168 by the wormshaft 178 varies the position of the hub member 170 with respect to thehub member 161 and accordingly varies the position of the pin 171 in theslot 172. Referring again to 'Fi 8 of the drawings, a suitable brake orfrlction device 179 pin 171 engages thev is mounted on the 'spindle 108in' order to prevent any overtravel of the spindle whenever thedirection of rotation thereof is reversed.

Referring to Figs. 14, 15 and 16 of the drawings, a third and thepreferred form of loose connection is illustrated. A disk 180, which iskeyed tothe shaft 106, is provided with two arcuated stop members' 181and 182. The sto member 181 is formed integral with the isk 180 whereasthe stop member 182 is adjustably secured to the disk by means of bolts183. The bolts 183 project through a slot 184 formed in the disk 180 andthe' stop member 182 is preferably fitted to a groove 185 in the disk.The end of the member 182 adjacent to the member 181 is provided with asurface 181a which is inclined with respect to the axis of the shaft.

The surface 186 of the stop member 181, which is adjacent to the stopmember 182, is parallel with the axis of the shaft. The work spindle 108carries a collar member 187 which is provided with a lug 188. The lug188 projects between the two stop members 181 and 182 on the disk 180 asshown in Figs. 14 and 16 of the drawings. The surface of the lug 188which engages the sto member 182 is inclined in accordance wit theinclination of the surface'181a of the stop member. The spindle 108carries a disk 189 having two pins 190 rejecting therefrom. The pins 190project t rough the collar member 187 and compel movement of the workcarrying spindle 108 in accordance with the rotation of the collarmember. An annular member 191, which is pivoted'at 192 on the carriage2, is provided with shoes 1.93 which are litted to a groove 194 in thecollar member 187 A worm segment 195, which is formed on the annularmember 191, as shown in Fi 15 of the drawings, is in engagement wit aworm shaft 196. The worm shaft 196 serves to effect movement of theannular member 191. When the shaft 106 is rotating in one direction, thestop member 182 engages the lug 188 to elfect rotation of the workcarrying spindle 108 and when the direction of rotation. of the shaft106 is reversed, the stop member 181 engages the lug 188 to eli'ectrotation of the spindle 108. Accordingly a rough adjustment of the looseconnection may be effected by adjusting the position of the stop member182 with respect to the stop member 101. A finer adjustment of the looseconnection is effected by varying the position of the lug 188 withrespect to the stop members 181 and 182. The axial position of the lug188 along the shaft 106 is varied by operating the worm shaft 196.

Modications in the mechanism and in the arrangement and location ofparts maybe made within the spirit and scope of our invention and suchmodifications are intended to be covered by the appended claims.

What we claim is: j

1. In a machine, the combination with al lead screw, a spindle, and atrain of gears for rotating said spindle and the lead screw in a forwardand 1n a reverse direction, of means for so connecting the spindle tothe train ofgearin@r as to insure a limited rotation of the lead screwprior ,'to the rotation of the spindle upon change in the operation ofthe gearing to change the direction of rotation of the lead screw andthe spindle.

2. In a machine, the combination with a lead screw, a work spindle, acarriage for the work spindle, a lead screw for operating said carriage,and means comprising a train of ears for rotating said spindle and thelea screw in a forward and 1n a reverse direction, of means for soconnectingA the s indle to said train of gears as to insure a imitedrotation of the lead screw prior to the rotation of the spindle uponchange in the operation of the train of gears to change the direction ofrotation of the lead screw and the spindle.

3. In a machine, the combination with a lead screw, a carri e operatedby vsaid lead screw, a work spin le mounted on said car-y riage, andmeans comprising a train of gears for rotating thespindle and the leadscrew in aI forward and in a reverse direction, of a lost motionconnection between the spindle and said train of gears to insure alimited rotation of the lead screw prior to the rotation of the spindleu on change in the operation of the traino gears to change the directionof rotation of the spindle and the lead screw, and means for l'varyingthe amount of said lost motion.

4. In a machine, the combination with a lead screw, a carriage operatedby the lead screw, a work carrying spindle, and means comprising a trainof gears for rotating the lead screw and the spindle in a forward and ina reverse direction, of a lost motion connection between said spindleand the gear train, and means for varying said tion connection to insurethe rotation of the spindle and the lead screw in the same relation whenrotating in a forward and in a reverse direction. l

5. In a machine, the combination with a lead screw, a carria e operatedby the lead screw, a work spind e mounted, on said carriage, saidspindle servin to carry a piece of work having a threa formed thereon,and means comprising a train of gears connected to the spindle and thelead screw for rotating them in timed relation, of a lost motionconnection 'oined to the gear train, and means for adjusting said lostmotion connection to compensate lfor the back lash in said gear 'trainwhereby the spindle and the lead screw may` be rotated in a forward 6.In a machine, the combination with two rotating members, and mechanismfor rotating the two members in timed relation to each other and forrotating the members in a forward and -in a reverse direction, of aloose connection between one of the members and the said mechanism tocompensate for the back lash in said mechanism upon reversal in thedirection of rotation of the members.

y7. In a machine, the combination with a work carrying spindle and alead screw for moving the work along a cutting tool, of a gear train forrotating the spindle and the screw in a forward an in a reversedirection, and a lost motion connection between one of said members andthe gear train to compensate for the back lash in the gear train.

8. In a machine, the combination with a work carrying spindle and a leadscrew for moving the work along a cutting tool, of a gear train forrotating the spindle and the screw in a forward and in a reversedirection, and a lost motion connection between the spindle and saidtrain of gears to compensate for the back lash in the gear train.

9. In a machine, the combination with a wiork carrying spindle, a leadscrew for effecting relative movement between the work and a cuttingtool, and means comprising a train of gear wheels for rotating the workspindle and the lead screw in a forward and in a reverse direction, of alost motion connection between said gear train and the spindle and leadscrew to compensate for the back lash in the gear train, saidconnectionfcomprising a lug member located between two stop members.

10. In a machine, the combination with a work carrying spindle, a leadscrew for effecting relative movement between the work and a cuttingtool, and means comprising a train of gear wheels for rotating the workspindle and the lead screw in a forward and in a reverse direction, of alost motion connection between said gear train and the spindle tocompensate for the back lash in the gear train, said connectioncomprising a lug member located between two stop memlbers, and means forvarying the relative position of the two stop members to vary the lostmotion in said connection.

11. In a machine, the combination with a work carrying spindle, a leadscrew for effecting relative movement between the work and a cuttingtool,A and means comprising a train of gear wheels for rotating the workspindle and the lead screw in a forward and in a reverse direction, of alost motion connection between said gear train and the spindle tocompensate for the back lash in the gear train, said connectioncomprising a lug member located between two stop members,

and means for varying the position of the lug and for varying therelative position of the two stop members to Vary fthe lost motion insaid connection.

12. In a machine, the combination with a work carrying'spindle, a leadscrew for4 spindle axis and for varying the relative position of the twostop members to vary,

the amount of lost motion in the connection. 13. In a machine, thecombination with a work carrying spindle, a lead screw for effectingrelative movement between the work and a cutting tool, and meanscomprising a train of gear wheels for rotating the spindle and the leadscrew in a forward and in a reverse direction, of a lost motionconnection between the work spindle and the gear train to compensate forthe back lash in the gear train, said connection comprising a lugrotating with the work spindle, two stop members rotating with said geartrain and respectively located on opposite sides of the lug member, andmeans for varying the relative position of the two stop members and forvarying the position of the lug along the spindle axis to vary theamount of lo motion in said connection.

14. In a machine, the combination with a work carrying spindle, a leadscrew4 for effecting relative movement between the workand the cuttingtool, and means comprising a'train of gear wheels for rotating the workspindle and the lead screw in a forward and in a reverse direction, of alost motion connection between the work spindle and lthe gear train,said connection comprising a lug rotating with the work spindle andprojecting between two stop members which rotate with said train of gearwheels, one of said stop members having a surface invarying the positionof the lug along the clined with respect to the spindle axis forengaging a similar surface on the lug and ward and in a reversedirection, of a lost to the spindle axis for engaging a similar motionconnection between the work spindle surface on said lug, and means forvarying and the gear train, said connection compristhe relative positionof the two stop meming a lug rotating with the work spindle bers and forvarying the position of the lug 5 and projecting between two stopmembers to vary the amount of lost motion in said 15 which rotatewithsaid train of `gear wheels, connection. one of said stop members having`a surface In testimony whereof, we hereto atiix our inclined withrespect to the spindle axis for signatures. engaging a similar surfaceon the lug and the CARL SCHRAMM.

10 other stop member having a surface parallel PAUL FRANK VOKAL.

